Field of the Invention
The present invention relates to a printed board and an image forming apparatus that is equipped with the printed board.
Description of the Related Art
An image forming apparatus such as a laser beam printer includes a charge device, a developing device, a transfer device and a fixing device. The charge device charges the surface of a photosensitive member to a uniform charge. The developing device develops a latent image that is formed on the photosensitive member by a laser beam or the like with toner. The transfer device transfers the developed toner image on the photosensitive member onto a transfer material. In addition, the fixing device includes a heater that is driven by an alternating current power supply, and heats the toner image that was transferred onto the transfer material to thereby fix the toner image on the transfer material.
A high voltage of several hundred volts to several kilovolts is applied to the charge device, the developing device and the transfer device. In order to supply a high voltage to these devices, the image forming apparatus is equipped with a high-voltage power supply board (hereunder, referred to as “power supply board”) having a high-voltage power supply circuit that generates a high voltage on a printed board. In a case where the power supply board and the main body of the image forming apparatus are connected using a high voltage cable in order to apply a high voltage generated by the power supply board to the charge device, the developing device and the transfer device, the assemblability is poor and costs are incurred in providing the high voltage cable. Therefore, for example, in Japanese Patent Application Laid-open No. 2002-158408, a method is proposed that connects a power supply board and the main body of an image forming apparatus without using a high voltage cable. That is, a conductive contact portion is provided on the power supply board, a coiled spring member is provided on the image forming apparatus main body side, and the power supply board is installed in the main body of the image forming apparatus. By this means, the contact portion on the power supply board and the coiled spring member on the image forming apparatus main body side come in contact, and a high voltage is applied to the image forming apparatus main body side. In addition, in Japanese Patent Application Laid-open No. 2002-158408, a configuration is adopted in which a hole is provided for confirming whether or not the spring member is contacting the contact portion of the power supply board after the power supply board has been installed in the main body of the image forming apparatus, and thus the state of contact therebetween can be visually checked.
However, according to the above described method that uses a coiled spring member to connect a power supply board provided inside an image forming apparatus and a contact point for input of a high voltage on the apparatus side, if the diameter of a coil portion of the spring member is reduced, the area thereof that contacts the printed board decreases. Consequently, when pushing the printed board against the spring member and fixing the printed board in that state, the contact state is unstable, and there is a high possibility that the spring member will be deformed. If the coil portion of the spring member is deformed, the coil portion will no longer precisely contact a circuit pattern on the power supply board side. Therefore, the diameter of the coil portion cannot be easily reduced. Consequently, there is the problem that the proportion of the area occupied by the contact point with respect to the overall power supply board increases, and this leads to an increase in the substrate area. Furthermore, there are many cases where a plurality of places that connect a power supply board and the main body of an image forming apparatus are provided, and in which a configuration is adopted so that a pressure contact force of a predetermined amount or more is applied to the contact portions to cause the respective contact portions to reliably contact. When installing the power supply board in the main body of the image forming apparatus, the power supply board directly receives a repulsive force of the spring member, and because the amount of force required when installing the power supply board increases as the number of contact portions increases, there is the problem that the assembly workability is poor.
In addition, there is also the problem that, depending on the size and quality of the material of the power supply board as well as the number of contact points, the power supply board itself may be bent by the repulsive force of the spring member, and stress may be applied to components that are mounted on the power supply board by such bending. Further, when visually checking the contact state through a hole for visual confirmation as described in the aforementioned Japanese Patent Application Laid-Open No. 2002-158408, one part of the spring member can be checked visually. However, there is also a problem that it is not possible to visually check whether a contact portion of the power supply board and a coil of the spring member securely contact each other.